A plastic bag is generally a bag made of thin, flexible, plastic sheet. Since the mid-1980's, the use of plastic bags for shopping has grown dramatically due to the great advantage plastic bags have over bags made of other materials, such as paper. There are many types of plastic bags, some of which are made of low or high density polyethylene (LDPE and HDPE, respectively). LDPE and HDPE bags are generally stronger, lighter and much more compact to store than paper bags. These properties make LDPE and HDPE bags less expensive to transport. LDPE and HDPE bags can be manufactured and sold at a fraction of the cost of competing paper bags, making them the bags of choice for retailers such as supermarkets and groceries stores.
Many plastic bags used by retailers are self-opening bags because of their conveniences. Many self-opening bag packs employ an adhesive means between consecutive bags so that pulling the first bag will also open the next bag behind the first one. In some self-opening bags, the adhesive means is a chemical adhesive such as glues or pressure sensitive adhesives. However, the use of chemical adhesive means may not be desirable in some applications.
In some applications, it is desirable that some self-opening bags are made of plastic materials that have an optimum amount of self-adhesion or blocking. If the amount of self-adhesion of the plastic materials is too large, it is difficult to have the bags self-open. On the other hand, if the amount of self-adhesion of the plastic materials is too low, each bag will detach from the next consecutive empty bag prematurely without pulling open the empty bag.
Currently, most of the self-opening bags can be made of a low density polyethylene such as low density polyethylene (LDPE) or linear low density polyethylene (LLDPE). It is well-known that LDPE and LLDPE films tend to self-adhere and the self-adhesion is generally too large for self-opening bag applications. On the other hand, the self-adhesion of high density polyethylene (HDPE) is generally too low for self-opening bag applications because HDPE does not tend to self-adhere.
For the foregoing reasons, there are needs for a polymer or polymer composition that can be used for making improved self-opening bag packs which can provide more reliable and consistent self-opening features than pure HDPE, LLDPE or LDPE bags. Further, there are needs for a polymer or polymer composition that has a lower self-adhesion property than that of LLDPE or LDPE and/or a higher self-adhesion property than that of HDPE.